My, What Big Claws! Dino Talons Used for Digging

Below:

Next story in Science

Giant, razor-sharp claws seen on herbivorous dinosaurs may have
been used for digging, grasping or piercing, a researcher says.

The new findings shed light on the changes in claw form and
function that occurred as birds evolved from their ancient
dinosaur ancestors, the scientist added.

Meat-eating dinosaurs such as Tyrannosaurus
rex and Velociraptor were all reptiles known as
theropods; they relied on sharp teeth and claws to capture and
kill prey. Many theropods may have possessed feathers, and
research suggests modern birds evolved from these dinosaurs.
[ In
Images: The Life of T. Rex ]

However, not all theropods were carnivores.

"The stereotypical image of theropod dinosaurs is that of large,
predatory and carnivorous animals," said study author Stephan
Lautenschlager, a vertebrate paleontologist at the University of
Bristol in England. "However, fossil findings in the last 15 to
20 years have shown that a number of different groups among
theropods did not conform to this classical view. Many of these
had apparently adapted to a different diet and become omnivores
or herbivores — that is evident from the shape of the teeth and
the morphology of the skull."

Lautenschlager investigated an unusual group of theropods known
as
therizinosaurs, which lived between 66 million and 145
million years ago in Asia and North America. These long-necked
dinosaurs, which possessed coats of primitive downlike feathers,
could reach up to 23 feet (7 meters) long with massive,
razor-sharp claws more than 19 inches (50 centimeters) in length.

"The large claws of Therizinosaurus cheloniformis have
been enigmatic since they were first discovered in the 1950s,"
Lautenschlager said. "Originally it was thought they belonged to
some sort of giant turtle. Later it became clear that they
belonged to the group of dinosaurs known as therizinosaurs, and
that other members of this group also had enlarged claws."

However, despite gigantic claws that might seem like ideal
weapons for killing prey, therizinosaurs were herbivores. To
understand how these plant eaters might have used their claws,
Lautenschlager digitally scanned the claws of 65 theropod species
and generated computer models to simulate how the dinosaurs might
have used such talons. He also compared those reptile talons with
claws from 40 mammal species, which scientists know the function
of.

Lautenschlager discovered therizinosaurs may have used their
giant claws for digging, grasping or piercing.

"The grasping function can roughly be compared with a rake or
grappling hook," Lautenschlager said. "These claws were probably
used to grasp a branch and pull it closer to the animal to reach
parts of the vegetation otherwise out of reach." The dinosaurs
may have used digging claws to unearth tasty roots.

Lautenschlager noted the changes seen in therizinosaur claws
paralleled changes seen in their skulls and teeth that helped the
animals adapt to changes in what they ate. This suggests changes
in theropod diet were major drivers for skeletal changes in
theropod evolution.

"Therizinosaurs were not directly ancestral to birds,"
Lautenschlager said. "Nevertheless, by understanding how
different dinosaurs adapted to different ecological situations —
for example, different food — we can better understand what
changes in the skeleton were related to diet, to flight or
something completely different."

Lautenschlagerdetailed his findings online May 7 in the journal
Proceedings of the Royal Society B.